The present invention relates to surgical stapling. More specifically, the invention relates to a surgical stapling instrument for use in microsurgery that stores a staple in a flexed and open state.
Surgical staples are well known in the art as fast and efficient wound closing devices. As such, they may either replace or complement retention sutures for joining adjacent body tissue. Typically, stapling instruments join adjacent body tissue by delivering a metal staple with a stapling gun. The stapling gun applies a mechanical force to permanently deform the staple from a generally U-shaped configuration to a final, closed configuration which holds the adjacent tissue together. Obviously, the force required to bend the staple must be applied at or adjacent the staple application site. As a result, these prior art staple guns require the positioning of relatively large and bulky mechanisms at the staple application site to produce and apply the required bending force to the staple.
Wound closure requires precise positioning of each staple to reduce tissue trauma, minimize blood loss, and achieve optimum cosmetic results. However, large, bulky staple guns are clumsy to control and reduce the accuracy with which a surgeon can position each staple. Further, since the bending force is required at the site of application, the necessary bulk of the gun at the staple application site limits the use of staples in many instances where their use would be otherwise desirable.
Hall et al U.S. Pat. No. 4,396,139 discloses a surgical staple gun that reduces the overall size and weight of the staple gun in order to provide more exacting control for the surgeon. The staple gun disclosed in Hall stores a plurality of resilient staples, each in a relaxed closed configuration. During delivery, a staple is flexed into an open crescent shape, and is released to return to its closed configuration while simultaneously piercing and drawing together adjacent edges of body tissue. The force required to flex each staple is much less than the force required to permanently deform the metal staples of the prior art. The overall size and weight of the staple gun can therefore be reduced.
However, the staple gun of Hall still requires a mechanical force near the tip of the gun (at the application site of the staple) to flex and release each staple. As a result, the staple gun is still large and clumsy. Further, the ejected staple tends to pinch the adjacent body tissue together, rather than holding the tissue together evenly while allowing the tissue to heal. Also, the expansion pins of Hall must be extricated after the staple is "closed" in the tissue.
Staple guns of the prior art are effective for rejoining a wide variety of tissue types and bones, such as the rib cage, fascia, muscle, skin and fat. These staple guns, however, are ineffective for use in microsurgery. Microsurgery applications include ophthalmology, otolaryngolical, neural, vascular, and intervascular surgery, among others. In cataract surgery, for example, the size of the staple may be two millimeters or less and must penetrate a distance less than one millimeter to avoid piercing the eyeball. Such small staples limit the use of clamping and bending tools. Further, the bulk of any conceivable bending tool limits accessibility in cases where surgery must be performed through very small and/or relatively deep openings.